JP6348765B2 - Microwave heat treatment apparatus and microwave heat treatment method - Google Patents

Description

  The present invention relates to a microwave heat treatment apparatus and a microwave heat treatment method for introducing a microwave into a processing container and performing heat treatment on a substrate.

  In recent years, an apparatus using a microwave has been proposed as an apparatus for performing a heat treatment on a substrate such as a semiconductor wafer. The heat treatment using microwaves is known to have a large process merit compared to conventional lamp heating type and resistance heating type annealing apparatuses because internal heating, local heating, and selective heating are possible. For example, when activation of doping atoms is performed using microwave heating, since the microwaves directly act on the doping atoms, there is an advantage that excessive heating does not occur and spreading of the diffusion layer can be suppressed. Furthermore, by using microwave irradiation, heat treatment can be performed at a relatively low temperature as compared with the conventional lamp heating method and resistance heating method, and an increase in thermal budget can be suppressed.

  As a heating device using microwaves, for example, Patent Document 1 discloses a microwave irradiation device in which conductive protrusions are unevenly distributed on the surface of a conductive guide plate for the purpose of uniformly heating an object to be processed. Proposed.

JP-A-3-233888 (for example, FIG. 1)

  The microwave has a feature that the wavelength is as long as several tens of millimeters and that a standing wave is easily formed in the processing container. Therefore, for example, when a semiconductor wafer is heat-treated with microwaves, there is a problem that the distribution of the intensity of the electromagnetic field is generated within the surface of the semiconductor wafer and the heating temperature is likely to be uneven.

  The present invention has been made in view of such problems, and an object thereof is to provide a microwave heat treatment apparatus and a microwave heat treatment method capable of performing uniform and efficient heat treatment on an object to be processed. There is to do.

The microwave heat treatment apparatus of the present invention has a top wall, a bottom wall and a side wall parallel to the top wall, and a processing container for storing a target object.
A microwave introduction device that generates microwaves for heat-treating the object to be treated and introduces the microwaves into one or more microwave introduction ports formed on the upper wall;
A holding portion for holding the object to be processed at a position facing the upper wall in the processing container by contacting the object to be processed;
It has. The microwave heat treatment apparatus of the present invention, by the holding unit,
The distance H1 from the upper surface of the bottom wall to the lower surface of the object to be processed is H1 <λ / 2 with respect to the wavelength λ of the microwave,
The object to be processed is held at a first height position where the distance H2 from the lower surface of the upper wall to the upper surface of the object to be processed is 3λ / 4 ≦ H2 <λ with respect to the wavelength λ of the microwave. Heat treatment.

The microwave heat treatment apparatus of the present invention further includes a height position adjusting device that variably adjusts the height position at which the holding unit holds the object to be processed.
During the heat treatment, the height position at which the object is held by the holding portion is switched from the second height position different from the first height position to the first height position. A control unit for controlling the height position adjusting device,
May be provided.

The microwave heat treatment apparatus of the present invention may further include a temperature measurement unit that measures the temperature of the object to be processed held by the holding unit,
The control unit may perform switching from the second height position to the first height position based on the temperature measured by the temperature measurement unit.

In the microwave heat treatment apparatus of the present invention, the object to be processed may be a silicon substrate,
The controller may switch from the second height position to the first height position when the temperature of the silicon substrate reaches 400 ° C. or higher in the heat treatment. Good.

The microwave heat treatment method of the present invention has an upper wall, a bottom wall and a side wall parallel to the upper wall, and one or more formed in the upper wall in a processing container that accommodates an object to be processed. Microwaves are introduced from a microwave introduction port to heat the object to be processed. In the microwave heat treatment method of the present invention, the distance H1 from the upper surface of the bottom wall to the lower surface of the object to be processed is H1 <λ / 2 with respect to the wavelength λ of the microwave,
The object to be processed is held at a first height position where the distance H2 from the lower surface of the upper wall to the upper surface of the object to be processed is 3λ / 4 ≦ H2 <λ with respect to the wavelength λ of the microwave. The heat treatment is performed.

  In the microwave heat treatment method of the present invention, in the middle of the heat treatment, the height position for holding the object to be processed is changed from the second height position different from the first height position to the first height position. You may switch to the height position.

  In the microwave heat treatment method of the present invention, switching from the second height position to the first height position may be performed based on the measured temperature of the workpiece.

In the microwave heat treatment method of the present invention, the object to be processed may be a silicon substrate,
In the heat treatment, when the temperature of the silicon substrate reaches 400 ° C. or higher, switching from the second height position to the first height position may be performed.

  In the microwave heat treatment apparatus and the treatment method of the present invention, it is possible to perform uniform and efficient heat treatment on an object to be processed.

It is sectional drawing which shows the schematic structure of the microwave heat processing apparatus used for the microwave heat processing method which concerns on one embodiment of this invention. It is a top view which shows the lower surface of the upper wall of the processing container shown in FIG. It is a perspective view of the holder which supports a to-be-processed object in the microwave heat processing apparatus shown in FIG. It is explanatory drawing which shows the height position of the holder in the processing container shown in FIG. It is explanatory drawing which shows the schematic structure of the high voltage power supply part of the microwave heat processing apparatus shown in FIG. It is a block diagram which shows the hardware constitutions of a control part. It is a flowchart which shows an example of the procedure of the microwave heat processing method which concerns on one implementation of this invention. It is a graph which shows the change of the carrier density in the temperature rising process of a silicon substrate. 2 is a graph showing changes in temperature and reflected waves when a semiconductor wafer is heat-treated in a microwave heat treatment apparatus having the same configuration as in FIG. 1. It is drawing which illustrates typically the height position of a semiconductor wafer in a processing container. It is another drawing which illustrates typically the height position of a semiconductor wafer in a processing container.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, with reference to FIG. 1, the microwave heat processing apparatus which concerns on one embodiment of this invention is demonstrated. FIG. 1 is a cross-sectional view showing a schematic configuration of a microwave heat treatment apparatus. FIG. 2 is a plan view showing the lower surface of the upper wall of the processing container shown in FIG. FIG. 3 is a perspective view of a holder as a holding unit that supports an object to be processed in the processing container of the microwave heat treatment apparatus shown in FIG. 1. FIG. 4 is an explanatory view showing the height position of the holder in the processing container shown in FIG. The microwave heat treatment apparatus 1 performs a heat treatment by irradiating a microwave on, for example, a semiconductor wafer for manufacturing a semiconductor device (hereinafter simply referred to as “wafer”) W with a plurality of continuous operations. It is a device to apply. Here, in the wafer W having a flat plate shape, the upper surface of the upper and lower surfaces having a large area is a semiconductor device formation surface, and this surface is a processing target.

  A microwave heat treatment apparatus 1 is opposed to a processing container 2 that accommodates a wafer W that is an object to be processed, a microwave introduction apparatus 3 that introduces microwaves into the processing container 2, and an upper wall 11 in the processing container 2. Each of the supporting device 4 that supports the wafer W at a position where it is positioned, the gas supply mechanism 5 that supplies gas into the processing vessel 2, the exhaust device 6 that evacuates the inside of the processing vessel 2, and the microwave heat treatment device 1 And a control unit 8 for controlling the components.

<Processing container>
The processing container 2 is made of a metal material. As a material for forming the processing container 2, for example, aluminum, aluminum alloy, stainless steel or the like is used. The microwave introduction device 3 is provided in the upper part of the processing container 2 and functions as a microwave introduction means for introducing electromagnetic waves (microwaves) into the processing container 2. The configuration of the microwave introduction device 3 will be described in detail later.

  The processing container 2 is provided so as to penetrate the upper and lower walls 11 and 4, four side wall portions 12 as side walls connecting the upper wall 11 and the bottom wall 13, and the upper wall 11. A plurality of microwave introduction ports 10, a loading / unloading port 12 a provided in the side wall portion 12, and an exhaust port 13 a provided in the bottom wall 13. Here, the four side wall portions 12 have a rectangular tube shape in which a horizontal cross section is connected at a right angle. Therefore, the processing container 2 has a cubic shape with a hollow inside. Moreover, the inner surface of each side wall part 12 is all flat and has a function as a reflecting surface for reflecting microwaves. The loading / unloading port 12a is for loading / unloading the wafer W to / from a transfer chamber (not shown) adjacent to the processing container 2. A gate valve GV is provided between the processing container 2 and a transfer chamber (not shown). The gate valve GV has a function of opening and closing the loading / unloading port 12a, and the processing container 2 is hermetically sealed in the closed state, and the wafer W can be transferred between the processing container 2 and a transfer chamber (not shown) in the open state. To.

<Supporting device>
As shown in FIGS. 1 and 3, the support device 4 is attached to the upper end of the shaft 14 and a tubular shaft 14 that extends through substantially the center of the bottom wall 13 of the processing vessel 2 to the outside of the processing vessel 2. And a holder 15 as a holding portion. The holder 15 includes a holder base portion 15a attached to the upper end of the shaft 14, a plurality of (three in this embodiment) arm portions 15b provided radially from the holder base portion 15a, and each arm portion. And a support pin 16 detachably attached to 15b. The plurality of support pins 16 support the wafer W by contacting the lower surface of the wafer W in the processing container 2. The plurality of support pins 16 are arranged so that their upper ends are aligned in the circumferential direction of the wafer W. Each support pin 16 is detachably attached to the arm portion 15b. The number of arm portions 15b and support pins 16 is not particularly limited as long as the wafer W can be stably supported. The holder 15 is made of a dielectric material. For example, quartz or ceramics can be used as the dielectric material for forming them.

  Furthermore, the support device 4 supports the shaft 14, the rotation drive unit 17 that rotates the shaft 14, the vertical drive unit 18 that displaces the shaft 14 up and down, and connects the rotary drive unit 17 and the lift drive unit 18. And a movable connecting portion 19 to be operated. The rotation drive unit 17, the elevating drive unit 18, and the movable connection unit 19 are provided outside the processing container 2. When the inside of the processing container 2 is in a vacuum state, a sealing device 20 such as a bellows can be provided around a portion where the shaft 14 penetrates the bottom wall 13.

  In the support device 4, the shaft 14, the holder 15, the rotation drive unit 17, and the movable connection unit 19 constitute a rotation device that rotates the wafer W in the horizontal direction. The holder 15 is rotated about the shaft 14 by driving the rotation driving unit 17 to cause each support pin 16 to circularly move (revolve) in the horizontal direction. The rotation drive unit 17 is not particularly limited as long as it can rotate the shaft 14, and may include, for example, a motor (not shown).

  In the support device 4, the shaft 14, the holder 15, the elevating driving unit 18, and the movable connecting unit 19 constitute a height position adjusting device that adjusts the height position of the wafer W. The holder 15 is configured to move up and down in the vertical direction together with the shaft 14 by driving the elevating drive unit 18. The raising / lowering drive part 18 will not be restrict | limited especially if the shaft 14 and the movable connection part 19 can be displaced up and down, For example, you may provide the ball screw etc. which are not shown in figure.

  In the microwave heat treatment apparatus 1 of the present embodiment, the holder 15 of the support apparatus 4 can hold the wafer W at a predetermined height. The height position for holding the wafer W by the holder 15 can be variably adjusted. For example, referring to FIG. 4, the holder 15 has a distance H1 from the upper surface of the bottom wall 13 to the lower surface of the wafer W with respect to the vacuum wavelength λ of the microwave (hereinafter sometimes simply referred to as “wavelength”) λ. , H1 <λ / 2, and the wafer W can be held at a height where the distance H2 from the lower surface of the upper wall 11 to the upper surface of the wafer W satisfies 3λ / 4 ≦ H2 <λ. This height position is the first height position in the present invention. If the thickness of the wafer W (about 0.6 mm) is ignored, the sum of the distance H1 and the distance H2 is the total height H of the processing container 2 (that is, from the lower surface of the upper wall 11 to the bottom wall 13). Equal to the distance to the top surface).

  At the first height position, by setting the distance H1 to be less than λ / 2, for example, in the temperature range of 400 ° C. or higher, the lower space S2 of the wafer W (the space from the upper surface of the bottom wall 13 to the lower surface of the wafer W). In addition, a standing wave having a wavelength in the height direction of the processing container 2 (hereinafter sometimes referred to as a “standing wave in the height direction”) is not generated. In the lower space S2 of the wafer W, a standing wave other than the standing wave in the height direction, for example, a standing wave in a direction parallel to the upper surface and the lower surface of the wafer W may be generated. In the present embodiment, the distance H1 is set to H1 <λ / 2, and the occurrence of standing waves in the height direction in the lower space S2 of the wafer W is prevented, so that the types of standing waves in the lower space S2 of the wafer W are reduced. By reducing, fluctuations in the standing wave can be avoided as much as possible.

  Further, at the first height position, by setting the distance H2 within the range of 3λ / 4 or more and less than λ, the upper space S1 of the wafer W (from the lower surface of the upper wall 11 to the wafer in a temperature range of 400 ° C. or more, for example). The generation of one standing wave in the height direction in the space up to the upper surface of W is allowed. Thus, the microwaves introduced from the microwave introduction ports 10 of the upper wall 11 are efficiently irradiated toward the wafer W in the upper space S1 of the wafer W. In addition, by setting 3λ / 4 ≦ H2 <λ, the microwave easily travels in a direction parallel to the upper surface of the wafer W, and shortens the wavelength of the standing wave in the direction parallel to the upper surface of the wafer W. Can do. Therefore, the wafer W can be heated uniformly at the antinode where the electric field is strong, and the uniformity of the heating temperature within the surface of the wafer W can be improved.

  The fluctuation of the standing wave in the space above and below the wafer W becomes an obstacle to the uniformity of the heating temperature in the plane of the wafer W. In the microwave heat treatment apparatus 1 of the present embodiment, by holding the wafer W at the first height position by the holder 15, the behavior of standing waves in the space above and below the wafer W is controlled, and those Variations can be suppressed and the uniformity of the heating temperature within the surface of the wafer W can be enhanced.

  Further, the holder 15 can take any height position other than the first height position. For example, as the second height position, a height position where the distance H1 from the upper surface of the bottom wall 13 to the lower surface of the wafer W and the distance H2 from the lower surface of the upper wall 11 to the upper surface of the wafer W are equal (H1 = H2 ) Can hold the wafer W. This height position is an intermediate position between the upper wall 11 and the bottom wall 13 in the processing container 2 (hereinafter, referred to as “intermediate position”). At the intermediate position, for example, the wafer W can be placed at the antinode of the standing wave where the electric field strength is strong in the processing chamber 2 in the temperature range of room temperature or more and less than 400 ° C. Therefore, the heating efficiency of the wafer W is improved. The temperature increase rate can be improved.

  Note that the rotation device that rotates the wafer W in the horizontal direction and the height position adjustment device that adjusts the height position of the wafer W may have other configurations as long as these objects can be realized. Further, the rotation driving unit 17 and the lifting / lowering driving unit 18 may be an integrated mechanism or may be configured without the movable connecting unit 19.

<Exhaust device>
The exhaust device 6 has, for example, a vacuum pump such as a dry pump. The microwave heat treatment apparatus 1 further includes an exhaust pipe 21 that connects the exhaust port 13 a and the exhaust apparatus 6, and a pressure adjustment valve 22 provided in the middle of the exhaust pipe 21. By operating the vacuum pump of the exhaust device 6, the internal space of the processing container 2 is evacuated under reduced pressure. In addition, the microwave heat processing apparatus 1 can also process by atmospheric pressure, and a vacuum pump is unnecessary in that case. Instead of using a vacuum pump such as a dry pump as the exhaust device 6, it is also possible to use an exhaust facility provided in a facility where the microwave heat treatment apparatus 1 is installed.

<Gas supply mechanism>
The microwave heat treatment apparatus 1 further includes a gas supply mechanism 5 that supplies gas into the processing container 2. The gas supply mechanism 5 includes a gas supply device 5a having a gas supply source (not shown), a plurality of pipes 23 (only two are shown) that are connected to the gas supply device 5a and introduce processing gas into the processing container 2. It has. The plurality of pipes 23 are connected to the side wall portion 12 of the processing container 2.

The gas supply device 5 a can supply, for example, a gas such as N ₂ , Ar, He, Ne, O ₂ , or H ₂ into the processing container 2 through the plurality of pipes 23 by the side flow method. It is configured. Note that the gas supply into the processing container 2 may be performed by providing a gas supply unit at a position (for example, the upper wall 11) facing the wafer W, for example. Moreover, you may use the external gas supply apparatus which is not contained in the structure of the microwave heat processing apparatus 1 instead of the gas supply apparatus 5a. Although not shown, the microwave heat treatment apparatus 1 further includes a mass flow controller and an opening / closing valve provided in the middle of the pipe 23. The types of gases supplied into the processing container 2 and the flow rates of these gases are controlled by a mass flow controller and an opening / closing valve.

<Temperature measurement unit>
The microwave heat treatment apparatus 1 further includes a plurality of radiation thermometers 26 that measure the surface temperature of the wafer W, and a temperature measurement unit 27 that is connected to the plurality of radiation thermometers 26. In FIG. 1, a plurality of radiation thermometers 26 are omitted except for the radiation thermometer 26 that measures the surface temperature of the central portion of the wafer W.

<Microwave radiation space>
In the microwave heat treatment apparatus 1 of the present embodiment, a space defined by the upper wall 11, the four side wall portions 12, and the bottom wall 13 in the processing container 2 forms a microwave radiation space. In this microwave radiation space, microwaves are radiated from a plurality of microwave introduction ports 10 provided on the upper wall 11. Since the upper wall 11, the four side walls 12, and the bottom wall 13 of the processing container 2 are all made of a metal material, the microwave is reflected and scattered in the microwave radiation space.

<Microwave introduction device>
Next, the configuration of the microwave introduction device 3 will be described with reference to FIGS. 1, 2, and 5. FIG. 5 is an explanatory diagram showing a schematic configuration of a high-voltage power supply unit of the microwave introduction device 3. As described above, the microwave introduction device 3 is provided in the upper part of the processing container 2 and functions as a microwave introduction unit that introduces electromagnetic waves (microwaves) into the processing container 2. As illustrated in FIG. 1, the microwave introduction device 3 includes a plurality of microwave units 30 that introduce microwaves into the processing container 2, and a high-voltage power supply unit 40 that is connected to the plurality of microwave units 30. ing.

(Microwave unit)
In the present embodiment, the configurations of the plurality of microwave units 30 are all the same. Each microwave unit 30 includes a magnetron 31 that generates a microwave for processing the wafer W, a waveguide 32 that serves as a transmission path for transmitting the microwave generated in the magnetron 31 to the processing container 2, and a microwave. And a transmission window 33 fixed to the upper wall 11 so as to close the introduction port 10. The magnetron 31 corresponds to the microwave source in the present invention.

  As shown in FIG. 2, in the present embodiment, the processing container 2 has four microwave introduction ports 10 arranged at equal intervals in the circumferential direction on the upper wall 11. Each microwave introduction port 10 has a rectangular shape in plan view having a long side and a short side. The size of each microwave introduction port 10 and the ratio between the long side and the short side may be different for each microwave introduction port 10, but the viewpoint of improving the uniformity of the heat treatment on the wafer W and improving the controllability. Therefore, it is preferable that all the four microwave introduction ports 10 have the same size and shape. In the present embodiment, a microwave unit 30 is connected to each microwave introduction port 10. That is, the number of microwave units 30 is four.

  The magnetron 31 has an anode and a cathode (both not shown) to which a high voltage supplied by the high voltage power supply unit 40 is applied. Further, as the magnetron 31, those capable of oscillating microwaves of various frequencies can be used. For the microwave generated by the magnetron 31, an optimum frequency is selected for each treatment of the object to be processed. For example, in the heat treatment, it is preferably a microwave having a high frequency such as 2.45 GHz, 5.8 GHz, A microwave of 5.8 GHz is particularly preferable.

  The waveguide 32 has a rectangular cross section and a rectangular tube shape, and extends upward from the upper surface of the upper wall 11 of the processing container 2. The magnetron 31 is connected in the vicinity of the upper end portion of the waveguide 32. The lower end portion of the waveguide 32 is in contact with the upper surface of the transmission window 33. The microwave generated in the magnetron 31 is introduced into the processing container 2 through the waveguide 32 and the transmission window 33.

  The transmission window 33 is made of a dielectric material. As a material of the transmission window 33, for example, quartz, ceramics, or the like can be used. A space between the transmission window 33 and the upper wall 11 is hermetically sealed by a seal member (not shown).

  The microwave unit 30 further includes a circulator 34, a detector 35 and a tuner 36 provided in the middle of the waveguide 32, and a dummy load 37 connected to the circulator 34. The circulator 34, the detector 35, and the tuner 36 are provided in this order from the upper end side of the waveguide 32. The circulator 34 and the dummy load 37 constitute an isolator that separates the reflected wave from the processing container 2. That is, the circulator 34 guides the reflected wave from the processing container 2 to the dummy load 37, and the dummy load 37 converts the reflected wave guided by the circulator 34 into heat.

  The detector 35 is for detecting a reflected wave from the processing container 2 in the waveguide 32. The detector 35 is configured by, for example, an impedance monitor, specifically, a standing wave monitor that detects an electric field of a standing wave in the waveguide 32. The standing wave monitor can be constituted by, for example, three pins protruding into the internal space of the waveguide 32. By detecting the location, phase and intensity of the electric field of the standing wave with the standing wave monitor, the reflected wave from the processing container 2 can be detected. Moreover, the detector 35 may be comprised by the directional coupler which can detect a traveling wave and a reflected wave.

  The tuner 36 has a function of performing impedance matching between the magnetron 31 and the processing container 2. Matching by the tuner 36 is performed based on the detection result of the reflected wave in the detector 35. The tuner 36 can be constituted by a conductor plate (not shown) provided so as to be able to be taken in and out of the internal space of the waveguide 32, for example. In this case, it is possible to adjust the impedance between the magnetron 31 and the processing container 2 by controlling the amount of electric power of the reflected wave by controlling the protruding amount of the conductor plate into the internal space of the waveguide 32. it can.

(High voltage power supply)
The high voltage power supply unit 40 supplies a high voltage for generating a microwave to the magnetron 31. As shown in FIG. 5, the high voltage power supply unit 40 operates the AC-DC conversion circuit 41 connected to the commercial power supply, the switching circuit 42 connected to the AC-DC conversion circuit 41, and the operation of the switching circuit 42. It has a switching controller 43 to be controlled, a step-up transformer 44 connected to the switching circuit 42, and a rectifier circuit 45 connected to the step-up transformer 44. The magnetron 31 is connected to the step-up transformer 44 via the rectifier circuit 45.

  The AC-DC conversion circuit 41 is a circuit that rectifies alternating current (for example, three-phase 200 V alternating current) from a commercial power source and converts it into direct current having a predetermined waveform. The switching circuit 42 is a circuit that controls on / off of the direct current converted by the AC-DC conversion circuit 41. In the switching circuit 42, a phase shift type PWM (Pulse Width Modulation) control or PAM (Pulse Amplitude Modulation) control is performed by the switching controller 43 to generate a pulsed voltage waveform. The step-up transformer 44 boosts the voltage waveform output from the switching circuit 42 to a predetermined magnitude. The rectifier circuit 45 is a circuit that rectifies the voltage boosted by the step-up transformer 44 and supplies the rectified voltage to the magnetron 31.

<Control unit>
Each component of the microwave heat treatment apparatus 1 is connected to the control unit 8 and controlled by the control unit 8. The control unit 8 is typically a computer. FIG. 6 illustrates an example of a hardware configuration of the control unit 8 illustrated in FIG. The control unit 8 includes a main control unit 101, an input device 102 such as a keyboard and a mouse, an output device 103 such as a printer, a display device 104, a storage device 105, an external interface 106, and a bus that interconnects them. 107. The main control unit 101 includes a CPU (Central Processing Unit) 111, a RAM (Random Access Memory) 112, and a ROM (Read Only Memory) 113. The storage device 105 is not particularly limited as long as it can store information, but is, for example, a hard disk device or an optical disk device. The storage device 105 records information on a computer-readable recording medium 115 and reads information from the recording medium 115. The recording medium 115 may be of any form as long as it can store information. For example, the recording medium 115 is a hard disk, an optical disk, a flash memory, or the like. The recording medium 115 may be a recording medium that records a recipe for the plasma etching method according to the present embodiment.

  In the control unit 8, the CPU 111 uses the RAM 112 as a work area to execute a program stored in the ROM 113 or the storage device 105, thereby performing a heating process on the wafer W in the microwave heating apparatus 1 of the present embodiment. It can be executed. Specifically, the control unit 8 relates to process conditions such as the temperature of the wafer W, the pressure in the processing container 2, the gas flow rate, the microwave output, and the rotation speed of the wafer W in the microwave heat treatment apparatus 1. Each component (for example, the microwave introduction apparatus 3, the support apparatus 4, the gas supply apparatus 5a, the exhaust apparatus 6, etc.) is controlled.

  In the microwave heat treatment apparatus 1 having the above configuration, variation in the heating temperature within the surface of the wafer W can be suppressed, and uniform heat treatment can be performed.

  The microwave heat treatment apparatus 1 can be preferably used for the purpose of heat treatment for activating the doping atoms implanted in the diffusion layer, for example, in a semiconductor device manufacturing process.

[Microwave heat treatment method]
Next, a preferred embodiment of the microwave heat treatment method performed in the microwave heat treatment apparatus 1 will be described.

<First Embodiment>
First, the microwave heat treatment method according to the first embodiment of the present invention performed in the microwave heat treatment apparatus 1 will be described. In the present embodiment, for example, a command is input from the input device 102 of the control unit 8 so that the microwave heat treatment apparatus 1 performs the heat treatment. Next, in response to this command, the main control unit 101 reads a recipe stored in the storage device 105 or the computer-readable recording medium 115. Next, each end device of the microwave heat treatment apparatus 1 (for example, the microwave introduction apparatus 3, the support apparatus 4, the gas supply apparatus 5a, and the like) from the main control unit 101 so that the heat treatment is performed according to the conditions based on the recipe. A control signal is sent to the exhaust device 6 or the like.

  Next, the gate valve GV is opened, and the wafer W is loaded into the processing container 2 through the gate valve GV and the loading / unloading port 12a by a transfer device (not shown), and the plurality of support pins 16 of the holder 15 are loaded. Placed on top.

  The holder 15 is moved up and down together with the shaft 14 by driving the elevating drive unit 18, and the wafer W is set at a predetermined height position. Here, in the present embodiment, the distance H1 from the upper surface of the bottom wall 13 to the lower surface of the wafer W is H1 <λ / 2 with respect to the wavelength λ, and from the lower surface of the upper wall 11 to the upper surface of the wafer W. The wafer W is placed at a height where the distance H2 satisfies 3λ / 4 ≦ H2 <λ with respect to the wavelength λ of the microwave. This height position corresponds to the first height position in the present invention.

  At the first height position, by setting the distance H1 to H1 <λ / 2, for example, in the temperature range of 400 ° C. or higher, the standing wave in the height direction of the processing chamber 2 in the lower space S2 of the wafer W can be obtained. Occurrence can be prevented. In the present embodiment, by preventing the occurrence of standing waves in the height direction in the lower space S2 of the wafer W, fluctuations in the standing waves in the lower space S2 of the wafer W can be avoided as much as possible.

  Further, at the first height position, the distance H2 is set to 3λ / 4 ≦ H2 <λ, so that, for example, in the temperature range of 400 ° C. or higher, the height direction standing in the upper space S1 of the wafer W is set. Allow one wave to be generated. Thus, the microwaves introduced from the microwave introduction ports 10 of the upper wall 11 are efficiently irradiated toward the wafer W in the upper space S1 of the wafer W. Also. By setting the distance H2 to 3λ / 4 ≦ H2 <λ, the wavelength of the standing wave in the direction parallel to the upper surface of the wafer W can be shortened, and the uniformity of the heating temperature within the surface of the wafer W can be improved. it can.

  The fluctuation of the standing wave in the space above and below the wafer W becomes an obstacle to the uniformity of the heating temperature in the plane of the wafer W. At the first height position, the behavior of the standing wave in the space above and below the wafer W is controlled, and the fluctuation thereof is reduced, so that the uniformity of the heating temperature in the plane of the wafer W can be improved. .

  In addition, it is preferable to rotate the wafer W at a predetermined speed in the horizontal direction by driving the rotation drive unit 17 as necessary at the first height position. The rotation of the wafer W may not be continuous but discontinuous. Next, the gate valve GV is closed, and if necessary, the inside of the processing container 2 is evacuated and exhausted by the exhaust device 6. Next, a processing gas having a predetermined flow rate is introduced into the processing container 2 by the gas supply device 5a. The internal space of the processing container 2 is adjusted to a predetermined pressure by adjusting the exhaust amount and the gas supply amount.

  Next, under the control of the control unit 8, a voltage is applied from the high voltage power supply unit 40 to the magnetron 31 to generate a microwave. The microwave generated in the magnetron 31 propagates through the waveguide 32, then passes through the transmission window 33, and is introduced into the space above the wafer W in the processing chamber 2. For example, microwaves are sequentially generated in the plurality of magnetrons 31, and the microwaves are alternately introduced into the processing container 2 from the microwave introduction ports 10. Note that a plurality of microwaves may be simultaneously generated in the plurality of magnetrons 31 and the microwaves may be simultaneously introduced into the processing container 2 from the respective microwave introduction ports 10.

  The microwave introduced into the processing container 2 is irradiated onto the wafer W, and the wafer W is rapidly heated by electromagnetic wave heating such as Joule heating, magnetic heating, and induction heating. As a result, the wafer W is subjected to a heat treatment. In the microwave heat treatment apparatus 1 of the present embodiment, the distance H1 from the upper surface of the bottom wall 13 to the lower surface of the wafer W satisfies H1 <λ / 2, and the distance from the lower surface of the upper wall 11 to the upper surface of the wafer W. By disposing the wafer W at a height position where H2 satisfies 3λ / 4 ≦ H2 <λ, a uniform heat treatment can be performed within the surface of the wafer W. Further, when the wafer W is rotated during the heat treatment, it is possible to reduce the bias of the microwave in the circumferential direction of the wafer W and to make the heating temperature in the wafer W surface more uniform. The rotation of the wafer W may not be continuous but discontinuous. If necessary, the inside of the processing container 2 may be evacuated by the exhaust device 6. Further, if necessary, the processing gas may be introduced into the processing container 2 by the gas supply device 5a. The internal space of the processing container 2 can be adjusted to a predetermined pressure by adjusting the exhaust amount and the supply amount of the processing gas.

  When a control signal for terminating the heat treatment is sent from the main control unit 101 to each end device of the microwave heat treatment apparatus 1, the generation of microwaves is stopped and the rotation of the wafer W is stopped. The supply is stopped, and the heat treatment for the wafer W is completed.

  After the heat treatment for a predetermined time or the cooling treatment after the heat treatment is completed, the gate valve GV is opened, the height position of the wafer W is adjusted by the support device 4, and the wafer W is then moved by the transfer device (not shown). Is carried out.

  As described above, in the microwave heat treatment method of the present embodiment, the influence of standing wave fluctuations is obtained by performing heat treatment by irradiating the wafer W held at a predetermined height position with microwaves. And a uniform heat treatment within the surface of the wafer W becomes possible.

<Second Embodiment>
Next, a microwave heat treatment method according to the second embodiment of the present invention performed in the microwave heat treatment apparatus 1 will be described. FIG. 7 is a flowchart illustrating an example of the procedure of the microwave heat treatment method of the present embodiment. As shown in FIG. 7, the microwave heat treatment method of the present embodiment includes steps S11 to S14.

  In the present embodiment, for example, a command is input from the input device 102 of the control unit 8 so that the microwave heat treatment apparatus 1 performs the heat treatment. Next, in response to this command, the main control unit 101 reads a recipe stored in the storage device 105 or the computer-readable recording medium 115. Next, each end device of the microwave heat treatment apparatus 1 (for example, the microwave introduction apparatus 3, the support apparatus 4, the gas supply apparatus 5a, and the like) from the main control unit 101 so that the heat treatment is performed according to the conditions based on the recipe. A control signal is sent to the exhaust device 6 or the like. Next, the gate valve GV is opened, and the wafer W is loaded into the processing container 2 through the gate valve GV and the loading / unloading port 12a by a transfer device (not shown), and the plurality of support pins 16 of the holder 15 are loaded. Placed on top.

(Step S11)
First, in step S11, the holder 15 holding the wafer W is displaced up and down by the elevating drive unit 18 of the support device 4 to adjust the wafer W to a predetermined height position. This height position may be a height position different from the first height position in step S13 described later. In the microwave heat treatment method of the present embodiment, an intermediate position (H1 = the distance H1 from the upper surface of the bottom wall 13 to the lower surface of the wafer W and the distance H2 from the lower surface of the upper wall 11 to the upper surface of the wafer W are equal). The wafer W can be placed on H2). This height position corresponds to the “second height position” in the present invention. In the second height position, for example, in the temperature range within the range of room temperature to less than 400 ° C., the wafer W can be placed at the antinode position of the standing wave having a strong electric field strength in the electromagnetic field distribution in the processing container 2. Therefore, the dielectric heating effect of the wafer W can be improved.

(Step S12)
Next, in step S <b> 12, the microwave is introduced into the processing container 2 by the microwave introduction device 3 while the wafer W is held at the second height position. Then, heat treatment is performed by irradiating the wafer W held at the second height position with microwaves. Specifically, under the control of the control unit 8, a voltage is applied from the high voltage power supply unit 40 to the magnetron 31 to generate a microwave. The microwave generated in the magnetron 31 propagates through the waveguide 32, further passes through the transmission window 33, and is introduced into a space above the rotating wafer W in the processing container 2. In the present embodiment, microwaves are sequentially generated in the plurality of magnetrons 31, and the microwaves are alternately introduced into the processing container 2 from the respective microwave introduction ports 10. Note that a plurality of microwaves may be simultaneously generated in the plurality of magnetrons 31 and the microwaves may be simultaneously introduced into the processing container 2 from the respective microwave introduction ports 10.

  The microwave introduced into the processing container 2 is irradiated onto the wafer W, and the wafer W is rapidly heated by electromagnetic wave heating such as Joule heating, magnetic heating, and induction heating. As a result, the wafer W is subjected to a heat treatment.

  By rotating the wafer W during the heat treatment, the bias of the microwave irradiated to the wafer W can be reduced, and the heating temperature within the surface of the wafer W can be made uniform. The rotation of the wafer W may not be continuous but discontinuous. If necessary, the inside of the processing container 2 may be evacuated by the exhaust device 6. Further, if necessary, the processing gas may be introduced into the processing container 2 by the gas supply device 5a. The internal space of the processing container 2 can be adjusted to a predetermined pressure by adjusting the exhaust amount and the supply amount of the processing gas.

(Step S13)
In step S13, the holder 15 is displaced by driving the elevating drive unit 18 while continuing the microwave irradiation to the wafer W, and the wafer W is switched from the second height position to the first height position. . At the first height position, by setting the distance H1 to H1 <λ / 2, for example, in the temperature range of 400 ° C. or higher, the standing wave in the height direction of the processing chamber 2 in the lower space S2 of the wafer W can be obtained. Occurrence can be prevented. In the present embodiment, by preventing the occurrence of standing waves in the height direction in the lower space S2 of the wafer W, fluctuations in the standing waves in the lower space S2 of the wafer W can be avoided as much as possible.

  Further, at the first height position, the distance H2 is set to 3λ / 4 ≦ H2 <λ, so that a standing wave in the height direction in the upper space S1 of the wafer W is one in a temperature range of 400 ° C. or more, for example. It is allowed to occur. Thus, the microwaves introduced from the microwave introduction ports 10 of the upper wall 11 are efficiently irradiated toward the wafer W in the upper space S1 of the wafer W. Also. By setting the distance H2 to 3λ / 4 ≦ H2 <λ, the wavelength of the standing wave in the direction parallel to the upper surface of the wafer W can be shortened, and the uniformity of the heating temperature within the surface of the wafer W can be improved. it can.

  The transition from step S12 to step S13 (that is, the timing of switching from the second height position to the first height position) can be performed based on the temperature of the wafer W measured by the temperature measurement unit 27, for example. it can. Specifically, the main control unit 101 of the control unit 8 monitors the measurement temperature information of the temperature measurement unit 27, and when the temperature of the wafer W reaches a predetermined temperature range, the process proceeds from step S12 to step S13. What is necessary is just to send a control signal to the raising / lowering drive part 18 so that it may perform. Further, the transition from step S12 to step S13 may be performed on the basis of a preset time based on, for example, experimentally obtained measurement data of the wafer W temperature. Here, the transition from step S12 to step S13 is performed when the temperature of the wafer W is, for example, 400 ° C. or higher, preferably 400 ° C. or higher and 600 ° C. or lower, more preferably 400 ° C. or higher and 500 ° C. or lower. It is good. In the temperature range of 400 ° C. or higher, silicon constituting the wafer W behaves as a conductor, and the wafer W becomes a reflection surface. Therefore, microwaves are separated in the upper space S1 and the lower space S2 of the wafer W in the processing container 2. Shows behavior. At the first height position, it is possible to suppress the occurrence of a standing wave in the height direction in the lower space S2 of the wafer W, and it is possible to minimize the fluctuation of the standing wave. At the first height position, in the upper space S1 of the wafer W, the wavelength of the standing wave in the direction parallel to the upper surface of the wafer W is shortened, and the uniformity of the heating temperature in the surface of the wafer W is improved. Can be increased. Therefore, when the temperature of the wafer W is 400 ° C. or more, the uniformity of the heating temperature within the surface of the wafer W can be improved by switching to the first height position. When the temperature of the wafer W is lower than 400 ° C., most of the microwaves pass through the wafer W because silicon constituting the wafer W hardly behaves as a conductor. As a result, the standing wave formed in the upper space S1 and the lower space S2 and its distribution are different from the case where the temperature of the wafer W is 400 ° C. or higher. Therefore, the height position of the wafer W in the temperature region in which silicon behaves as a conductor is an important factor for performing uniform processing within the surface of the wafer W.

  The processing conditions in step S13 are the same as those in step S12 except that the height position of the wafer W is changed to the first height position.

(Step S14)
Next, in step S14, the supply of microwaves is stopped. For example, by sending a control signal for ending the heat treatment from the main control unit 101 to each end device of the microwave heat treatment apparatus 1, the generation of microwaves is stopped and the rotation of the wafer W is stopped. The supply of gas is stopped, and the heat treatment for the wafer W is completed.

  After the heat treatment for a predetermined time or the cooling treatment after the heat treatment is completed, the gate valve GV is opened, the height position of the wafer W is adjusted by the support device 4, and the wafer W is then moved by the transfer device (not shown). Is carried out.

  As described above, in the microwave heat treatment method of the present embodiment, the wafer W is irradiated with microwaves and the height position of the wafer W is switched in the middle of performing the heat treatment, whereby the standing in the processing container 2 is performed. It is possible to perform the heat treatment on the wafer W in a state where the wave behavior is controlled and the microwave utilization efficiency is high. In particular, when the temperature of the wafer W is less than 400 ° C., the heat treatment is performed at the second height position, and when the temperature is 400 ° C. or more, the heat treatment is performed by switching to the first height position, thereby improving the dielectric heating effect and the wafer. Uniformity of processing within the plane of W can be achieved. The height position of the wafer W is not limited to two stages, and may be switched to three or more stages. Further, when switching the height position of the wafer W, the supply of microwaves may be temporarily stopped.

<Action>
Next, the operation of the present invention will be described with reference to FIGS. First, FIG. 8 is a graph showing a change in carrier density during a temperature rising process in which a silicon substrate doped with a dopant at a general concentration is heated. Semiconductors usually increase in electrical conductivity with increasing temperature. In the graph of FIG. 8, from the room temperature to about 127 ° C. is a payout area having a constant conductivity. When the temperature rises above 127 ° C., the electrical conductivity increases with a significant increase in carriers and becomes an intrinsic region. Accordingly, it is considered that the silicon constituting the wafer W enhances the property as a conductor in the temperature range of 400 ° C. or higher.

  FIG. 9 shows a change in temperature and a change in reflected wave power when the wafer W is heat-treated in the microwave heat treatment apparatus 1 having the same configuration as in FIG. In this experiment, four magnetrons 31 generate 5.8 GHz microwaves with an output of 1000 W each, and the temperature of the wafer W when each microwave is introduced into the processing chamber 2 from each microwave introduction port 10 and each temperature. The reflected wave power to the microwave introduction port 10 was measured. The upper graph in FIG. 9 shows the temperature change in the central portion of the wafer W, the peripheral portion, and the intermediate portion between the central portion and the peripheral portion. The lower graph shows the reflected wave power to the four microwave introduction ports 10 (in FIG. 9, the microwave introduction ports are represented as 10A, 10B, 10C, and 10D). In FIG. 9, while the temperature of the wafer W rises from about 300 ° C. to about 500 ° C. over about 15 to 20 seconds from the start of temperature rise (which means the timing at which the reflected wave power is generated), the symbol t It can be seen that the behavior of the reflected wave changes greatly from the time point shown. This indicates that, for example, when the temperature is raised to 400 ° C. or higher, the silicon constituting the wafer W behaves as a conductor.

  The processing container 2 is surrounded by an upper wall 11, a side wall portion 12, and a bottom wall 13. Therefore, the microwave introduced into the processing container 2 forms a standing wave in the processing container 2 in a direction parallel to the upper or lower surface of the wafer W and in the height direction of the processing container 2. Here, when attention is paid to the standing wave generated in the height direction in the processing chamber 2, when the temperature of the wafer W is less than 400 ° C., the silicon constituting the wafer W behaves as a semiconductor, so that the microwave passes through the wafer W. Then, one standing wave having the same wavelength as the height H is generated in the height direction of the processing container 2. Therefore, when the temperature of the wafer W is less than 400 ° C., the intermediate position between the top wall 11 and the bottom wall 13 in the processing container 2 is the position of the antinode of the standing wave with strong electric field strength. Therefore, the dielectric heating efficiency of the wafer W can be maximized by setting the height position of the wafer W to an intermediate position where the distance H1 and the distance H2 are equal, for example, as shown in FIG.

  On the other hand, when the temperature of the wafer W is 400 ° C. or higher, for example, the wafer W behaves in the same manner as a metal with respect to a microwave of 5.8 GHz, so that the wafer W becomes a metal interface and reflection of the microwave occurs. Therefore, standing waves are generated in the upper space S1 and the lower space S2 of the wafer W, respectively. Here, when a standing wave in the height direction is generated in the lower space S2 of the wafer W, the fluctuation of the standing wave is likely to occur due to the arm portion 15b and the shaft 15 of the holder 15 disposed below the wafer W, and the wafer There is a concern of reducing the uniformity of the heating temperature in the plane of W. Therefore, in the microwave heat treatment apparatus 1 of the present embodiment, as shown in FIG. 11, the height in the lower space S2 is set by placing the wafer W at the first height position where H1 <λ / 2. Generation of standing waves in the direction is prevented, and fluctuations in standing waves are avoided. Specifically, when a microwave of 5.8 GHz is used, the vacuum wavelength λ is about 51.7 mm, so the distance H1 may be less than 25.84 mm.

  Further, at the first height position where 3λ / 4 ≦ H2 <λ, one standing wave in the height direction is allowed to be generated in the upper space S1 of the wafer W. As a result, the direction of the electric field of the microwave introduced from each microwave introduction port 10 of the upper wall 11 approaches the height direction of the processing container 2, so that the microwave is efficiently irradiated toward the wafer W. Further, by setting 3λ / 4 ≦ H2 <λ, the wavelength of the standing wave in the direction parallel to the upper surface of the wafer W can be shortened, so that the uniformity of the heating temperature within the surface of the wafer W can be improved. Can be increased. Specifically, when a microwave of 5.8 GHz is used, the distance H2 may be set in the range of 38.77 mm or more and 51.7 mm or less.

  In addition, this invention is not limited to the said embodiment, A various change is possible. For example, the number of microwave units 30 (the number of magnetrons 31) and the number of microwave introduction ports 10 in the microwave heat treatment apparatus are not limited to the numbers described in the above embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Microwave heat processing apparatus, 2 ... Processing container, 3 ... Microwave introduction apparatus, 4 ... Support apparatus, 5 ... Gas supply mechanism, 5a ... Gas supply apparatus, 6 ... Exhaust apparatus, 8 ... Control part, 10 ... Micro Wave introduction port, 12 ... side wall, 14 ... shaft, 15 ... holder, 15a ... holder base, 15b ... arm, 16 ... support pin, 17 ... rotary drive, 18 ... lift drive, 30 ... microwave unit, DESCRIPTION OF SYMBOLS 31 ... Magnetron, 32 ... Waveguide, 33 ... Transmission window, 34 ... Circulator, 35 ... Detector, 36 ... Tuner, 37 ... Dummy load, 40 ... High voltage power supply part, W ... Semiconductor wafer.

Claims (4)

A processing container having an upper wall, a bottom wall and a side wall parallel to the upper wall, and containing an object to be processed;
A microwave introduction device that generates microwaves for heat-treating the object to be treated and introduces the microwaves into one or more microwave introduction ports formed on the upper wall;
A holding portion for holding the object to be processed at a position facing the upper wall in the processing container by contacting the object to be processed;
A height position adjusting device that variably adjusts a height position at which the holding unit holds the object to be processed;
A temperature measuring unit for measuring the temperature of the object to be processed held in the holding unit;
A control unit for controlling the height position adjusting device;
With
By the holding part,
The distance H1 from the upper surface of the bottom wall to the lower surface of the object to be processed is H1 <λ / 2 with respect to the wavelength λ of the microwave,
The object to be processed is held at a first height position where the distance H2 from the lower surface of the upper wall to the upper surface of the object to be processed is 3λ / 4 ≦ H2 <λ with respect to the wavelength λ of the microwave. Heat treatment,
The control unit determines a height position at which the object to be processed is held by the holding part during the heating process based on the temperature measured by the temperature measurement unit , as the first height position. The microwave heat processing apparatus which performs control which switches from the 2nd height position different from 1st to the said 1st height position . The object to be processed is a silicon substrate;
The control unit performs switching from the second height position to the first height position when the temperature of the silicon substrate reaches 400 ° C. or higher in the heat treatment. The microwave heat processing apparatus of description. A microwave is introduced from one or a plurality of microwave introduction ports formed in the upper wall into a processing container having an upper wall, a bottom wall and a side wall parallel to the upper wall, and containing an object to be processed. A microwave heat treatment method for performing heat treatment of the object to be processed,
The distance H1 from the upper surface of the bottom wall to the lower surface of the object to be processed is H1 <λ / 2 with respect to the wavelength λ of the microwave,
The object to be processed is held at a first height position where the distance H2 from the lower surface of the upper wall to the upper surface of the object to be processed is 3λ / 4 ≦ H2 <λ with respect to the wavelength λ of the microwave. Heat treatment,
Based on the measured temperature of the object to be processed, a height position for holding the object to be processed is changed from the second height position different from the first height position in the middle of the heat treatment from the first height position. A microwave heat treatment method characterized by switching to a height position. The object to be processed is a silicon substrate;
4. The microwave heating according to claim 3, wherein, in the heat treatment, when the temperature of the silicon substrate reaches 400 ° C. or higher, switching from the second height position to the first height position is performed. 5. Processing method.

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